Hikers and backpackers usually require a shelter such as a tent for overnight or multi-night trips. The longer the trip, the greater the need for a shelter of as little packed weight as possible to reduce fatigue, to make room for food and other gear in the pack, and to increase the enjoyment of hiking. But striking the proper balance between reducing the shelter's weight for carrying, while maintaining or increasing its shelter value (ease of set-up, weather resistance, sturdiness, roominess, ventilation, and other factors known to those skilled in the art) is a constant challenge.
Both single- and double-wall tents and shelters have benefited in recent years from the advent of lighter, stronger fabrics for the weatherproof canopy or “fly” portion and (for double-wall tents) the inner-tent portion; and from lighter, stronger poles. Another development has been the introduction of lightweight single-wall shelters primarily consisting of silicone-impregnated nylon or “silnylon” canopies supported by various combinations of trekking and/or arch poles, sometimes floorless but increasingly with insect netting and floors. My own Tarptent™ line of shelters found at www.tarptent.com has included a number of inventive and patented shelter designs using single-wall silnylon canopies, including those disclosed in U.S. Pat. Nos. 7,406,977; 7,146,996; and 7,134,443.
Much of a shelter's weight is concentrated in its poles and reducing pole weight is a key factor in designing lightweight shelters with high space/weight ratios. However, high space/weight ratios are difficult to achieve without compromising stability, useable space, or both. Inwardly sloping walls cut off useable space and long, unsupported fabric spans are inherently less stable than those supported by closely spaced poles. Arch poles maximize interior space and fabric support but are about 3 times heavier than vertical poles of the same height as the arch. Typical dome or tunnel tents require at least two such arch poles. Hence, erecting a shelter can be a time-consuming and complex process requiring pole assembly followed by clipping or threading the pole(s) to the shelter fabric. In a raging storm, time to erect one's shelter is of critical importance.
Single pole shelters—single arch or single vertical pole—minimize weight and setup time but compromise useable space at the canopy edges furthest from the pole. Edges and corners can be raised a few inches above ground with long stakes or long guylines but such edges slope to near ground level, cutting off useable space, and the further the edge from a fixed support, the lower the stability. Another method for both raising and stabilizing the edge is the use of a corner support such as a vertical “strut.” If short enough, the strut can be integrated into the canopy structure and rolled up with the shelter for storage, never needing to be reassembled in the field. When held in tension via staking, struts lift and provide direct support (see Hilleberg Atko, Terra Nova Laser, or Tarptent Contrail). Technically, such a structure is no longer single-pole but additional complexity and setup time is minimized while useable space is dramatically improved. However, single struts are only moderately stable without multiple guy lines running from the strut apex to the ground. A single vertical pole (or strut) must have at least 3 equally spaced and angled lines of tension to become stable and thus a single strut at a tent corner isn't stable enough to limit all motion, especially in strong wind.
In view of the above-noted shortcomings of single-arch tents, the standards for “four-season” tents able to withstand severe weather remain multi-pole geodesic or paraboloid designs with multiple crossing poles, and tunnel tents relying on premium-strength poles and canopy fabrics to withstand snow loading. But dome and tunnel type four-season tents tend to be relatively heavy, and in the case of geodesic dome and paraboloid tents they also tend to have lower space-to-weight ratios due to the low-angled curvature of the tent fabric at the sides. Another problem is that strong, multi-pole four-season tents are often regarded as “dedicated” winter tents, being too heavy and complicated to carry and use for the other three seasons of backpacking, when weather is less severe and shelter requirements are reduced.
One type of light, four-season tent of as little weight as possible is the Hilleberg Akto tent, a one-man shelter with a single arch pole bisecting a narrow hexagonal canopy with rectangular walled ends. The walled ends are lower than the center arch, with the end wall corners raised on short straight rods (four total) to provide extra height. While the Akto is generally well regarded for all-around use, its single arch has been reported as being less than ideal for significant snow loading and severe wind, and it is not freestanding. There is no fabric support between the central arch and corners to withstand significant snow, and the single corner struts lack stability.
Accordingly, until now there does not appear to have been a lightweight arch-supported tent capable of withstanding “four season” snow loading and winds while being equally practical and light enough for three-season use. What is needed is a tent shelter with additional pole support when needed for snow loading and severe wind, but where one or more poles can be left at home to save significant weight during less extreme weather. What is also needed is a lightweight support device, in conjunction with a larger support such as a main, central arch, to raise and support the fabric in order to maximize useable space and stability without the need for additional arch poles, and to minimize complexity and risk of breakage.